The present invention relates to a method of applying a liquid composite substance to a continuously moving web in manufacturing a photographic photosensitive material such as a photographic film and printing paper, a photoengraving material or a recording material such as pressure-sensitive recording paper and thermosensitive recording paper. More particularly, the invention relates to a method of simultaneously applying liquid substances as two or more mutually-overlaid layers to a continuously moving web.
A method of rapid simultaneous multilayer application in a slide-hopper-type application device or the like was disclosed in the U.S. Pat. No. 4,001,024. In order to increase the application speed in the method, a liquid substance having a viscosity as low as 1 cps to 8 cps is applied as the lowermost layer to a web to set the degree of wet application of the liquid substance at 2 cm.sup.3 to 12 cm.sup.3 per 1 m.sup.2 of the surface of the web. A meniscoid vortical movement is allowed only to mix the lowermost layer and the second lowermost layer with each other but not allowed to affect the other layers.
A method of applying to a web a thin carrier layer of a pseudo-plastic liquid substance of 20 cps to 200 cps in viscosity at the shear rate of 100 sec.sup.-1 and 10 cps or less in viscosity at the shear rate of 100,000 sec.sup.-1 was disclosed in the U.S. Pat. No. 4,113,903. In the method, the pseudo-plastic liquid substance whose viscosity is high at the low shear rate and low at the high shear rate is used as the lowermost layer on the web in order to eliminate the instability of an application bead, as in the method disclosed in the U.S. Pat. No. 4,001,024. The liquid substance is characterized in that it performs non-Newtonian flow. The liquid substance needs to be a selected special composite substance and subjected to careful preparation.